Large acenes find a growing number of applications in organic electronics. However their applicability is limited by their poor solubility and their inherent instability. One strategy widely exploited in order to overcome these limitations is the inclusion of appropriate substituents that increase both stability and solubility of acene derivatives.
Another less explored way of “protecting” acenes consists of the preparation of partially hydrogenated analogues, which has been carried out by partial hydrogenation of polycyclic aromatic hydrocarbons or by reduction of the corresponding quinones.
There are different ways to obtain the partially hydrogenated polyacenes.
In the document titled Linear Acene Derivatives. New routes to pentacene and naphthacene and the first synthesis of a triptycene with two anthracene moieties, Jihmei Luo and Harold Hart, the Journal of organic chemistry, vol. 52, no 22, Oct. 30, 1987, 4833-4836; is described the synthesis of 5,14-dihydropentacene. Benzocyclobutene was heated with anthracene 1,4-endoxine in toluene and after a dehydration step with an acid the 5,14 dihydropentacene is obtained.
In the document titled Fullerene-Acene Chemistry: diastereoselective synthesis of a cis,cis-tris[60]fullerene adduct of 6,8,15,17-tetraphenylheptacene, Glen P. Miller and Jonanthan Briggs, Organic letters, 2003, vol. 5 no 22, 4203-4206 is described the synthesis of 5,7,9,14,16,18-hexahydro-6,8,15,17-tetraphenylheptacene. The 1,3-diphenylnaphthol[2,3-c]-furan reacts with p-benzoquinone, then a double dehydration with p-toluene sulfonic acid in benzene affords 6,8,15,17-tetraphenylheptacene-7,16-quinone, the reduction of this compound with hydriodic acid in acetic acid gives the 5,7,9,14,16,18-hexahydro-6,8,15,17-tetraphenylheptacene.
In the document titled Divergent gold (I) catalyzed skeletal rearrangements of 1,7 enynes, Rebecca Meiβ, Kamal Kumar and Herbert Waldmann Chem. Eur. J. 2015, 21, 13526-13530 is described the divergent skeletal rearrangement of 1,7-enynes into exocyclic allenes and tricyclic hexahydroanthracenes by catalysis with a cationic gold(I) complex. In this document are obtained tricyclic substituted hexahydroanthracenes, not dihydrotetracenes. The reaction only occurs with aromatic derivatives having at least two alkoxy substituents. Also the conditions of the process are extreme and low yields are reported.
Thus, from what is known in the art, it is derived that the development of a process for the production of partially hydrogenated polyacenes and the corresponding polyacenes that show high yield is still of great interest.